Axial Gap-Type Motor, Blower, and Air Conditioner

This is a continuation of International Application No. PCT/JP2024/018933 filed on May 23, 2024, which claims priority under 35 U.S.C. § 119(a) to Patent Application No. 2023-109473, filed in Japan on Jul. 3, 2023, all of which are hereby expressly incorporated by reference into the present application.

The present disclosure relates to an axial gap-type motor, a blower, and an air conditioner.

Conventionally, as disclosed in JP 2006-353078 A, an axial gap-type motor including a rotor and a stator facing the rotor across an air gap in an axial direction of the rotor is known.

An axial gap-type motor according to a first aspect includes a rotor and a stator. The rotor has a disk shape. The stator faces the rotor across an air gap in an axial direction of the rotor. The stator includes a plurality of stator cores and a coil wound around each of the stator cores. A plurality of the stator cores is annularly arranged when viewed from the axial direction of the rotor. The rotor has a plurality of through holes penetrating in the axial direction of the rotor. The plurality of through holes is provided on a radially inner side of the rotor with respect to the coil when viewed from the axial direction of the rotor.

100 100 A bloweraccording to a first embodiment of the present disclosure is used in, for example, an air conditioner. In this case, the air conditioner includes an indoor unit including the blowerand an outdoor unit connected to the indoor unit via a refrigerant circuit. The refrigerant circuit includes a compressor, a four-way switching valve, an outdoor heat exchanger, an electric expansion valve, an indoor heat exchanger, and an accumulator.

1 FIG. 100 10 20 30 40 20 30 As shown in, the blowerincludes a housing, a first fan, a second fan, and a motor. The first fanand the second fanare, for example, centrifugal fans such as sirocco fans.

10 10 20 30 10 10 10 13 11 10 12 10 14 11 12 14 11 10 10 10 10 15 10 a b a a a a c a b a b. 1 FIG. The housingincludes a cylindrical portionthat accommodates the first fanand the second fan, and a blow-out portionprotruding from the cylindrical portion. In a longitudinal direction of the cylindrical portion, a flangehaving a first suction portis provided at one end of the cylindrical portion, and a flange (not shown) having a second suction portis provided at the other end of the cylindrical portion. A bell mouthis provided in the first suction portand the second suction port. In, only the bell mouthin the first suction portis shown. An annular motor fixing portionis provided along a peripheral direction on an outer periphery of a central portion in the longitudinal direction of the cylindrical portion. The blow-out portionhas a quadrangular pyramid shape that gradually expands outward along the peripheral direction of the cylindrical portion. A blow-out portis provided at an outer end of the blow-out portion

2 4 FIGS.to 20 21 22 23 22 21 21 23 22 21 As shown in, the first fanincludes a disk-shaped end plate, a plurality of blades, and an annular member. The plurality of bladesare connected to one surface of the end plateand are arranged at intervals along a peripheral direction of the end plate. The annular memberis connected to an end of the plurality of bladeson an opposite side to a side to which the end plateis connected.

2 4 FIGS.to 30 31 32 33 32 31 31 33 32 31 As shown in, the second fanincludes a disk-shaped end plate, a plurality of blades, and an annular member. The plurality of bladesare connected to one surface of the end plateand are arranged at intervals along a peripheral direction of the end plate. The annular memberis connected to an end of the plurality of bladeson an opposite side to a side to which the end plateis connected.

40 40 50 60 70 50 60 70 50 60 4 FIG. The motoris an axial gap-type motor. As shown in, the motorincludes a disk-shaped first rotor, a disk-shaped second rotor, and a disk-shaped stator. Hereinafter, a direction along axes of the first rotorand the second rotoris referred to as an “axial direction”. The statoris disposed between the first rotorand the second rotorin the axial direction.

50 21 20 21 20 50 40 3 FIG. The first rotoris disposed to face the end plateof the first fan. As shown in, the end plateof the first fanis disposed in a non-contact state with the first rotorof the motor.

5 6 FIGS.and 5 FIG. 50 52 53 52 52 52 52 52 53 53 53 52 53 52 53 53 53 53 53 20 70 53 52 53 53 53 53 53 a a b a a a b a b As shown in, the first rotorincludes a bossand a magnet memberprovided on an outer periphery of the boss. The bossis molded from metal. The bosshas a cylindrical shape. The bosshas a circular holein its central portion. The magnet memberis molded from a plastic magnet. The magnet memberhas a disk shape. When the magnet memberis molded, the bossand the magnet memberare integrally molded by attaching the bossas an insert component to a mold. The magnet memberincludes a protrusionthat does not act as a magnet and a magnet portionthat acts as a magnet. The protrusionis a portion of the magnet memberthat protrudes in the axial direction on the first fanside and is recessed on the statorside. The protrusionhas a circular shape when viewed from the axial direction. The bossis located at a center of the protrusionwhen viewed from the axial direction. The magnet portionis located around the protrusionwhen viewed from the axial direction. In the magnet portion, as shown in, S poles and N poles are alternately arranged in a peripheral direction of the magnet member.

60 31 30 31 30 60 40 3 FIG. The second rotoris disposed to face the end plateof the second fan. As shown in, the end plateof the second fanis disposed in a non-contact state with the second rotorof the motor.

7 8 FIGS.and 7 FIG. 60 62 63 62 62 62 62 62 63 63 63 62 63 62 63 63 63 63 63 30 70 63 62 63 63 63 63 63 a a b a a a b a b As shown in, the second rotorincludes a bossand a magnet memberprovided on an outer periphery of the boss. The bossis molded from metal. The bosshas a cylindrical shape. The bosshas a circular holein its central portion. The magnet memberis molded from a plastic magnet. The magnet memberhas a disk shape. When the magnet memberis molded, the bossand the magnet memberare integrally molded by attaching the bossas an insert component to a mold. The magnet memberincludes a protrusionthat does not act as a magnet and a magnet portionthat acts as a magnet. The protrusionis a portion of the magnet memberthat protrudes in the axial direction on the second fanside and is recessed on the statorside. The protrusionhas a circular shape when viewed from the axial direction. The bossis located at a center of the protrusionwhen viewed from the axial direction. The magnet portionis located around the protrusionwhen viewed from the axial direction. In the magnet portion, as shown in, S poles and N poles are alternately arranged in a peripheral direction of the magnet member.

9 11 FIGS.to 70 71 72 73 74 75 76 77 78 As shown in, the statorincludes a plurality of stator cores, a plurality of coils, a shaft, a mold portion, an insulator, a first bearing, a second bearing, and a bearing housing.

71 70 72 71 75 71 72 The plurality of stator coresare annularly arranged at intervals along a peripheral direction of the statorwhen viewed from the axial direction. Each coilis formed by winding a winding wire around each stator core. The insulatorinsulates the stator corefrom the coil.

73 20 52 50 73 30 62 60 20 73 52 50 21 20 30 73 62 60 31 30 50 60 40 20 30 20 30 10 11 12 15 a a The shaftextends toward the first fanthrough the circular holeof the first rotoralong the axial direction. The shaftextends toward the second fanthrough the circular holeof the second rotoralong the axial direction. On the side of the first fan, the shaftis fixed to an inner peripheral surface of the bossof the first rotorand the end plateof the first fan. On the second fanside, the shaftis fixed to an inner peripheral surface of the bossof the second rotorand the end plateof the second fan. When the first rotorand the second rotorrotate around the axis during driving of the motor, the first fanand the second fanrotate around the axis. By the rotation of the first fanand the second fan, air outside the housingis sucked into the first suction portand the second suction portand discharged from the blow-out port.

74 71 72 74 74 74 74 74 10 10 a a c The mold portionis a disk-shaped member formed by resin molding so as to surround the stator coreand the coil. The mold portionhas an outer edge portionprotruding from a side surface of the mold portion. The outer edge portionof the mold portionis fixed by the motor fixing portionof the housing.

76 50 77 60 76 77 73 78 76 77 The first bearingis provided on the first rotorside in the axial direction. The second bearingis provided on the second rotorside in the axial direction. The first bearingand the second bearingrotatably support the shaft. The bearing housingaccommodates the first bearingand the second bearing.

11 FIG. 70 50 1 70 60 2 1 2 As shown in, the statorfaces the first rotoracross the first air gap Gin the axial direction. The statorfaces the second rotoracross the second air gap Gin the axial direction. The axial dimensions of the first air gap Gand the second air gap Gare, for example, 0.5 mm to 2 mm.

3 FIG. 11 FIG. 70 50 60 74 74 50 60 a As shown in, the outer diameter of the statoris larger than the outer diameter of the first rotorand the outer diameter of the second rotor. As shown in, the outer diameter of the mold portionexcluding the outer edge portionis substantially the same as the outer diameter of the first rotorand the outer diameter of the second rotor.

11 FIG. 74 70 20 53 50 74 70 30 63 60 As shown in, a central portion of the mold portionof the statorprotrudes in the axial direction on the first fanside in accordance with the shape of the magnet memberof the first rotor. The central portion of the mold portionof the statorprotrudes in the axial direction on the second fanside in accordance with the shape of the magnet memberof the second rotor.

50 54 54 53 53 54 50 72 54 50 21 1 a 11 FIG. The first rotorhas a plurality of through holespenetrating in the axial direction. The plurality of through holesare provided in the protrusionof the magnet member. As shown in, the plurality of through holesis provided on a radially inner side of the first rotorwith respect to the coilwhen viewed from the axial direction. The through holescommunicate a space between the first rotorand the end platewith the first air gap G.

5 FIG. 50 54 1 50 54 54 1 54 As shown in, the first rotorhas ten through holesarranged along a circumference of a first circle Ccentered on the axis of the first rotorwhen viewed from the axial direction. These through holeshave a circular shape and the same dimension (diameter) when viewed from the axial direction. The ten through holesare arranged at equal intervals along a circumferential direction of the first circle C. The diameter of the through holesis, for example, 2.5 mm.

54 1 50 1 52 53 50 52 53 50 72 5 FIG. 11 FIG. a a The plurality of through holesis provided in a circular first region Rcentered on the axis of the first rotorwhen viewed from the axial direction. In, the first region Ris substantially the same as a region occupied by the bossand the protrusionof the first rotor. As shown in, the bossand the protrusionare located on a radially inner side of the first rotorwith respect to the coil.

1 50 50 50 50 50 1 50 53 50 a The radius of the first region Ris 40% or less of the radius of the first rotor. The radius of the first rotoris a dimension from the axis of the first rotorto an outer edge of the first rotorwhen the first rotoris viewed from the axial direction. The radius of the first region Ris substantially equal to or smaller than the dimension from the axis of the first rotorto an outer edge of the protrusionwhen the first rotoris viewed from the axial direction.

1 50 1 50 1 50 The radius of the first region Rmay be 25% or less of the radius of the first rotor. Alternatively, the radius of the first region Rmay be 20% or less of the radius of the first rotor. Alternatively, the radius of the first region Rmay be 15% or less of the radius of the first rotor.

54 52 1 50 The plurality of through holesis provided outside the bosswhen viewed from the axial direction. Therefore, for example, the radius of the first region Ris preferably 5% or more of the radius of the first rotor.

60 64 64 63 63 64 60 72 64 60 31 2 a 11 FIG. The second rotorhas a plurality of through holespenetrating in the axial direction. The plurality of through holesare provided in the protrusionof the magnet member. As shown in, the plurality of through holesis provided on a radially inner side of the second rotorwith respect to the coilwhen viewed from the axial direction. The through holescommunicate a space between the second rotorand the end platewith the second air gap G.

7 FIG. 60 64 2 60 64 64 2 64 As shown in, the second rotorhas ten through holesarranged along a circumference of a second circle Ccentered on the axis of the second rotorwhen viewed from the axial direction. These through holeshave a circular shape and the same dimension (diameter) when viewed from the axial direction. The ten through holesare arranged at equal intervals along a circumferential direction of the second circle C. The diameter of the through holesis, for example, 2.5 mm.

64 2 60 7 2 62 63 60 62 63 60 72 a a 11 FIG. The plurality of through holesis provided in a circular second region Rcentered on the axis of the second rotorwhen viewed from the axial direction. In FIG., the second region Ris substantially the same as a region occupied by the bossand the protrusionof the second rotor. As shown in, the bossand the protrusionare located on a radially inner side of the second rotorwith respect to the coil.

2 60 60 60 60 60 2 60 63 60 a The radius of the second region Ris 40% or less of the radius of the second rotor. The radius of the second rotoris a dimension from the axis of the second rotorto an outer edge of the second rotorwhen the second rotoris viewed from the axial direction. The radius of the second region Ris substantially equal to or smaller than the dimension from the axis of the second rotorto an outer edge of the protrusionwhen the second rotoris viewed from the axial direction.

2 60 2 60 2 60 The radius of the second region Rmay be 25% or less of the radius of the second rotor. Alternatively, the radius of the second region Rmay be 20% or less of the radius of the second rotor. Alternatively, the radius of the second region Rmay be 15% or less of the radius of the second rotor.

64 62 2 60 The plurality of through holesis provided outside the bosswhen viewed from the axial direction. Therefore, for example, the radius of the second region Ris preferably 5% or more of the radius of the second rotor.

54 50 1 54 1 54 54 50 1 1 1 50 50 50 50 A first ratio, which is a ratio of a total area of the plurality of through holesof the first rotorto an opening area of an outer edge portion of the first air gap G, is 3% or more. The first ratio means a ratio of the total area of the plurality of through holesto the opening area of the outer edge portion of the first air gap G. The total area of the plurality of through holesis a total area occupied by the through holeswhen the first rotoris viewed from the axial direction. The opening area is an area occupied by the first air gap Gwhen the first air gap Gis viewed from a horizontal direction. The opening area is calculated by multiplying the axial dimension of the first air gap Gat the outer edge of the first rotorby the length of the outer edge of the first rotor. The length of the outer edge of the first rotoris calculated by multiplying the diameter of the first rotorwhen viewed from the axial direction by the circular constant.

The first ratio may be 10% or more. Alternatively, the first ratio may be 20% or more. The first ratio is preferably 40% or less.

64 60 2 64 64 60 2 2 2 60 60 60 60 A second ratio, which is a ratio of a total area of the plurality of through holesof the second rotorto an opening area of an outer edge portion of the second air gap G, is 3% or more. The total area of the plurality of through holesis a total area occupied by the through holeswhen the second rotoris viewed from the axial direction. The opening area is an area occupied by the second air gap Gwhen the second air gap Gis viewed from a horizontal direction. The opening area is calculated by multiplying the axial dimension of the second air gap Gat the outer edge of the second rotorby the length of the outer edge of the second rotor. The length of the outer edge of the second rotoris calculated by multiplying the diameter of the second rotorwhen viewed from the axial direction by the circular constant.

The second ratio may be 10% or more. Alternatively, the second ratio may be 20% or more. The second ratio is preferably 40% or less.

(4-1)

40 1 50 70 2 60 70 1 2 40 50 60 1 2 The axial gap-type motorhas the first air gap Gbetween the first rotorand the statorand the second air gap Gbetween the second rotorand the stator. The air gaps Gand Ghave natural frequencies. Therefore, during driving of the motor, due to minute vibration in the axial direction of the rotorsand, abnormal noise having a peak of a sound pressure level may occur at frequencies near the natural frequencies of the air gaps Gand G.

12 13 FIGS.and 1 1 1 1 show stationary waves having the natural frequency of the first air gap G. The stationary wave represents radial vibration of air in the first air gap G. In a case where the air in the first air gap Gis displaced radially outward, the amplitude of the stationary wave is positive. In a case where the air in the first air gap Gis displaced on the radially inner side, the amplitude of the stationary wave is negative.

1 50 54 2 50 54 12 FIG. 13 FIG. 12 13 FIGS.and A first wave Wshown inrepresents a stationary wave in a case where the first rotordoes not have the through hole. A second wave Wshown inrepresents a stationary wave in a case where the first rotorhas the through hole. In, the stationary wave indicated by the dotted line is 180° different in phase from the stationary wave indicated by the solid line.

50 54 40 1 55 1 1 55 1 50 50 54 1 55 1 54 2 55 1 54 2 1 1 54 1 50 1 1 50 12 FIG. 13 FIG. In a case where the first rotordoes not have the through hole, opening ends (a portion communicating with an external space of the motor) of the first air gap Gare only both endsof the first air gap G. Therefore, as shown in, the antinode (position where the amplitude is maximized) of the first wave Wis located only at both endsof the first air gap Gin the radial direction of the first rotor. On the other hand, in a case where the first rotorhas the through hole, the opening ends of the first air gap Gare both endsof the first air gap Gand the through hole. Therefore, as shown in, the antinode of the second wave Wis located at both endsof the first air gap Gand at a central portion where the through holeis located. Accordingly, the natural frequency of the second wave Wis about twice the natural frequency of the first wave W. In this manner, the natural frequency of the first air gap Gcan be changed by providing the through holenear a node (a position where the amplitude becomes 0) of the first wave Win the radial direction of the first rotor. The node of the first wave Wis located at the central portion of the first air gap Gin the radial direction of the first rotor.

14 FIG. 14 FIG. 14 FIG. 12 FIG. 13 FIG. 50 72 50 50 54 50 54 1 2 1 54 50 50 54 50 54 shows measurement data of the sound pressure level of the abnormal noise generated in a case where the first rotoris minutely vibrated by causing a minute current to flow through the coilwhile changing the frequency with a signal generator. The horizontal axis inrepresents the frequency of minute vibration of the first rotor. The vertical axis inrepresents the sound pressure level of the abnormal noise. First measurement data represents measurement data in a case where the first rotordoes not have the through hole. Second measurement data represents measurement data in a case where the first rotorhas the through hole. In the first measurement data, the natural frequency of the first wave Wshown inis about 1150 Hz. In the second measurement data, the natural frequency of the second wave Wshown inis about 2050 Hz. Therefore, as described above, it has been observed that the natural frequency of the first air gap Gbecomes about twice by providing the through holein the first rotor. It has been observed that the sound pressure level at the natural frequency of 1150 Hz in a case where the first rotorhas the through holeis lower than the sound pressure level at the natural frequency of 2050 Hz in a case where the first rotordoes not have the through hole.

40 54 50 1 1 64 60 2 2 Therefore, in the axial gap-type motor, by providing the plurality of through holesin a central portion of the first rotorand making the natural frequency of the first air gap Glarger than a predetermined frequency, the abnormal noise having the peak of the sound pressure level at a frequency near the natural frequency of the first air gap Gis reduced. Similarly, by providing the plurality of through holesin a central portion of the second rotorand making the natural frequency of the second air gap Glarger than a predetermined frequency, the abnormal noise having the peak of the sound pressure level at a frequency near the natural frequency of the second air gap Gis reduced.

15 FIG. 15 FIG. 40 50 60 54 64 50 60 54 64 54 64 50 60 shows an example of measurement data of noise generated in a case where the motoris driven. Third measurement data represents measurement data in a case where the rotorsanddo not have the through holesand. Fourth measurement data represents measurement data in a case where the rotorsandhave the through holesand. As shown in, it has been observed that the values of the plurality of peaks of the sound pressure level at the frequency around 1150 Hz decrease by providing the through holesandin the rotorsand.

40 54 64 50 60 40 Therefore, in the axial gap-type motor, by providing the through holesandin the rotorsand, abnormal noise generated from the motoris reduced.

(4-2)

1 2 50 60 1 2 54 64 1 2 By forming the opening ends of the air gaps Gand Gat the central portions of the rotorsand, the natural frequencies of the air gaps Gand Gbecome larger than a predetermined frequency, and the sound pressure level at a frequency near the natural frequencies decreases. Therefore, the degree of decrease in the sound pressure level at the frequency near the natural frequencies changes depending on the number, shape, and position of the through holesandwhich are the opening ends of the air gaps Gand G.

16 FIG. 16 FIG. 16 FIG. 16 FIG. 16 FIG. 54 50 54 50 54 54 54 54 54 54 16 54 50 54 64 60 54 50 shows measurement data indicating the relationship between the number of the through holesof the first rotorand the sound pressure level of the generated abnormal noise. The horizontal axis inrepresents the number of the through holes. The vertical axis inrepresents the sound pressure level at 1100 Hz. 1100 Hz is a frequency at which the sound pressure level of the abnormal noise generated in a case where the first rotordoes not have the through holeis maximized. The horizontal axis of the graph ofshows the correspondence relationship between the number of the through holesand the first ratio. Since all the through holeshave the same dimension, the first ratio is proportional to the number of the through holes. For example, in a case where the number of the through holesis 60, the first ratio is 40%, and in a case where the number of the through holesis 30, the first ratio is 20%. The first ratio of the measurement data ranges from 0% to 40%. FIG.shows measurement data in a case where the number of the through holesof the first rotoris 0, 5, 10, 20, 30, and 60. As shown in, in a case where the number of the through holesis 0, 5, 10, 20, 30, and 60, the first ratio is 0%, 3.3%, 6.7%, 13%, 20%, and 40%, respectively. The number, shape, and position of the through holesof the second rotorare the same as the number, shape, and position of the through holesof the first rotor. Therefore, the second ratio is the same as the first ratio.

16 FIG. 54 1 As shown in, it has been observed that the sound pressure level decreases as the first ratio, which is the ratio of the total area of the through holesto the opening area of the outer edge portion of the first air gap G, increases. As the first ratio increases from 0% to 20%, a significant decrease in the sound pressure level has been observed. Specifically, it has been confirmed that in a case where the first ratio is 3.3%, the sound pressure level is reduced by about 10 dB as compared with a case where the first ratio is 0%. It has been confirmed that in a case where the first ratio is 20%, the sound pressure level is reduced by about 20 dB as compared with a case where the first ratio is 0%. It has been observed that the sound pressure level does not substantially decrease as the first ratio increases from 20% to 40%.

50 50 50 50 16 FIG. When the first ratio exceeds 40%, the rigidity of the first rotordecreases, and there is a possibility that the vibration of the first rotorin the axial direction increases. Therefore, in order to ensure the rigidity of the first rotor, the first ratio is preferably as small as possible. On the other hand, in order to lower the sound pressure level, the first ratio is preferably as large as possible. As shown in, the first ratio is preferably 3.3% to 20%, more preferably 6.7% to 20%, and still more preferably 13% to 20% from the viewpoint of the rigidity of the first rotorand the decrease in the sound pressure level.

60 Similarly, in order to ensure the rigidity of the second rotor, the second ratio is preferably as small as possible. On the other hand, in order to lower the sound pressure level, the second ratio is preferably as large as possible. Therefore, similarly to the first ratio, the second ratio is preferably 3.3% to 20%, more preferably 6.7% to 20%, and still more preferably 13% to 20%.

40 54 64 50 60 40 50 60 Therefore, in the axial gap-type motor, by appropriately setting the first ratio and the second ratio and providing the through holesandin the rotorsand, it is possible to effectively reduce the abnormal noise generated from the motorwhile securing the rigidity of the rotorsand.

100 100 54 50 64 60 The bloweraccording to a second embodiment shares a basic configuration and operation with the bloweraccording to the first embodiment. The difference between the second embodiment and the first embodiment is the number and positions of the through holesof the first rotorand the through holesof the second rotor.

50 60 54 54 54 54 50 50 50 54 54 17 20 FIGS., g g In the present embodiment, the first rotorhasthrough holes. These through holeshave a circular shape and the same dimension (diameter) when viewed from the axial direction. As shown inthrough hole groupseach including three through holesdisposed along the radial direction of the first rotorare disposed along the peripheral direction of the first rotor. In order to ensure the rigidity of the first rotor, the radial positions of two through hole groupsadjacent to each other in the peripheral direction are different by about the diameter of the through hole.

64 60 54 50 The plurality of through holesof the second rotoris disposed at the same position as the plurality of through holesof the first rotor.

100 100 54 50 64 60 The bloweraccording to the third embodiment shares a basic configuration and operation with the bloweraccording to the first embodiment. The difference between the third embodiment and the first embodiment is the number and positions of the through holesof the first rotorand the through holesof the second rotor.

50 54 54 3 50 54 18 FIG. In the present embodiment, the first rotorhas ten through holes. As shown in, ten through holesare arranged along the circumference of a third circle Ccentered on the axis of the first rotorwhen viewed from the axial direction. These through holeshave a circular shape when viewed from the axial direction.

54 54 54 54 54 54 54 54 54 3 54 54 54 3 a b b a b a a b The ten through holesinclude two types of through holes having different sizes. The ten through holesinclude five first through holesand five second through holes. The diameter of the second through holeis larger than the diameter of the first through hole. For example, the diameter of the second through holeis 1.5 times the diameter of the first through hole. The ten through holesare arranged at equal intervals along a circumferential direction of the third circle C. The ten through holesare arranged such that the first through holesand the second through holesare alternately arranged along the circumferential direction of the third circle C.

54 50 40 In the present embodiment, since the two types of through holeshaving different sizes are alternately arranged in the circumferential direction, the rigidity of the first rotorcan be secured while reducing the abnormal noise generated from the motorby increasing the first ratio.

64 60 54 50 The plurality of through holesof the second rotoris disposed at the same position as the plurality of through holesof the first rotor.

100 100 54 50 64 60 The bloweraccording to the fourth embodiment shares a basic configuration and operation with the bloweraccording to the first embodiment. The difference between the fourth embodiment and the first embodiment is the number, shapes, and positions of the through holesof the first rotorand the through holesof the second rotor.

50 54 54 4 5 50 54 4 5 5 4 19 FIG. In the present embodiment, the first rotorhas 20 through holes. As shown in, a total of 20 through holesare arranged along the circumferences of a fourth circle Cand a fifth circle Ccentered on the axis of the first rotorwhen viewed from the axial direction. These through holeshave a substantially rectangular shape extending along a circumferential direction of the fourth circle Cand the fifth circle Cwhen viewed from the axial direction. The diameter of the fifth circle Cis larger than the diameter of the fourth circle C.

54 54 54 54 54 4 54 4 54 5 54 5 54 50 54 4 5 c d c c d d The 20 through holesinclude two types of through holes having different sizes. The 20 through holesinclude ten third through holesand ten fourth through holes. The ten third through holesare arranged at equal intervals along the circumferential direction of the fourth circle C. The center of the third through holeis located on the circumference of the fourth circle C. The ten fourth through holesare arranged at equal intervals along the circumferential direction of the fifth circle C. The center of the fourth through holeis located on the circumference of the fifth circle C. The center of the through holeis an intersection of a straight line that passes through the axis of the first rotorand divides the through holeinto two in the peripheral direction and the fourth circle Cor the fifth circle Cwhen viewed from the axial direction.

54 5 54 4 54 5 54 4 d c d c The dimension of the fourth through holein the circumferential direction of the fifth circle Cis larger than the dimension of the third through holein the circumferential direction of the fourth circle C. For example, the dimension of the fourth through holein the circumferential direction of the fifth circle Cis twice the dimension of the third through holein the circumferential direction of the fourth circle C.

54 4 5 40 In the present embodiment, since the through holehas a substantially rectangular shape extending along the circumferential direction of the fourth circle Cand the fifth circle C, it is possible to effectively reduce the abnormal noise generated from the motorby increasing the first ratio.

19 FIG. 54 50 54 54 50 54 54 50 d c c d As shown in, when viewed from the axial direction, the center of the fourth through holeis not located on a straight line connecting the axis of the first rotorand the center of the third through hole. Similarly, when viewed from the axial direction, the center of the third through holeis not located on a straight line connecting the axis of the first rotorand the center of the fourth through hole. By arranging the through holein this manner, rigidity of the first rotorcan be secured.

64 60 54 50 The plurality of through holesof the second rotoris disposed at the same position as the plurality of through holesof the first rotor.

40 50 60 70 40 50 100 20 30 20 In the above embodiment, the motorincludes a pair of the first rotorand the second rotorarranged on both sides in the axial direction of the stator. However, the motormay include only the first rotor. In this case, the blowermay include both the first fanand the second fan, or may include only the first fan.

20 30 In the above embodiment, the first fanand the second fanare, for example, sirocco fans. However, the above embodiment may be applied to a blower including another type of fan.

54 64 50 60 54 64 54 64 1 2 50 60 1 2 In a case where the plurality of through holesandare arranged side by side in the peripheral direction of the rotorsand, it is preferable that the through holesandare arranged such that the region occupied by the through holesandin the peripheral direction is as large as possible. In this case, the areas of the opening ends of the air gaps Gand Glocated in the central portions of the rotorsandincrease, and the natural frequencies of the air gaps Gand Gincrease, and the sound pressure level tends to decrease.

5 FIG. 54 1 54 1 54 1 1 54 64 50 60 Specifically, as shown in, in a case where the plurality of through holesis arranged along the circumference of the first circle Csuch that a center of each of the through holesis located on the circumference of the first circle C, a third ratio is preferably a predetermined value or more. The third ratio is a ratio of a total length of the plurality of through holesin the circumferential direction of the first circle Cto the length of the circumference of the first circle C. The third ratio increases as the region occupied by the through holesandin the peripheral direction of the rotorsandincreases. Therefore, the sound pressure level tends to decrease as the third ratio increases. The third ratio is preferably 0.1 or more, and more preferably 0.2 or more.

16 FIG. 54 50 54 54 shows measurement data in a case where the number of the through holesof the first rotoris 0, 5, 10, 20, 30, and 60. The shapes of the through holeswhen viewed from the axial direction are all circular. The dimensions of the through holesare all the same.

5 17 FIGS.and 54 54 54 54 show the arrangement of the through holesin cases where the number of the through holesis 10 and 60, respectively. Next, a specific example of the arrangement of the through holesin cases where the number of the through holesis 5, 20, and 30 will be described.

20 FIG. 54 54 50 54 6 50 54 6 shows the arrangement of the through holesin a case where the number of the through holesis 5. The first rotorhas five through holesdisposed along the circumference of a sixth circle Ccentered on the axis of the first rotorwhen viewed from the axial direction. The five through holesare arranged at equal intervals along a circumferential direction of the sixth circle C.

21 FIG. 54 54 50 54 7 8 50 8 7 54 7 54 8 shows the arrangement of the through holesin a case where the number of the through holesis 20. In the first rotor, a total of 20 through holesare arranged along the circumferences of a seventh circle Cand an eighth circle Ccentered on the axis of the first rotorwhen viewed from the axial direction. The diameter of the eighth circle Cis larger than the diameter of the seventh circle C. The ten through holesare arranged at equal intervals along a circumferential direction of the seventh circle C. The ten through holesare arranged at equal intervals along a circumferential direction of the eighth circle C.

54 8 50 54 7 54 7 50 54 8 When viewed from the axial direction, the center of the through holeon the eighth circle Cis not located on a straight line connecting the axis of the first rotorand the center of the through holeon the seventh circle C. Similarly, when viewed from the axial direction, the center of the through holeon the seventh circle Cis not located on a straight line connecting the axis of the first rotorand the center of the through holeon the eighth circle C.

54 7 The 20 through holesmay be arranged at equal intervals along the circumferential direction of the seventh circle C.

22 FIG. 54 54 50 54 9 10 50 10 9 54 9 54 10 shows the arrangement of the through holesin a case where the number of the through holesis 30. In the first rotor, a total of 30 through holesare arranged along the circumferences of a ninth circle Cand a tenth circle Ccentered on the axis of the first rotorwhen viewed from the axial direction. The diameter of the tenth circle Cis larger than the diameter of the ninth circle C. The 15 through holesare arranged at equal intervals along a circumferential direction of the ninth circle C. The 15 through holesare arranged at equal intervals along a circumferential direction of the tenth circle C.

54 10 50 54 9 54 9 50 54 10 When viewed from the axial direction, the center of the through holeon the tenth circle Cis not located on a straight line connecting the axis of the first rotorand the center of the through holeon the ninth circle C. Similarly, when viewed from the axial direction, the center of the through holeon the ninth circle Cis not located on a straight line connecting the axis of the first rotorand the center of the through holeon the tenth circle C.

54 9 The 30 through holesmay be arranged at equal intervals along the circumferential direction of the ninth circle C.

64 60 54 50 In this modification, the plurality of through holesof the second rotoris disposed at the same position as the plurality of through holesof the first rotor.

Although the embodiments of the present disclosure have been described above, it will be understood that various changes in form and details can be made without departing from the gist and scope of the present disclosure disclosed in claims.